The invention relates to yarn suitable for machine knitting and to safety garments made with the yarn.
Cut-resistant yarn utilizing stainless steel wire strands and high strength aramid strands, such as Kevlar made by E.I Dupont de Nemours Corp., and gloves made therefrom are shown in the Byrnes et al. U.S. Pat. No. 4,384,449 and in the Bettcher U.S. Pat. No. 4,470,251. These gloves have proven highly successful. Another fiber, a high strength stretched polyethylene fiber manufactured and marketed by Allied Corporation, Morris Township, Morris County, N.J., U.S.A., has also provided good cut resistance when used in place of aramid fiber. The Allied fiber is sold under the name Spectra and is described in detail in U.S. Pat. No. 4,413,110 to Kavesh et al. Applicant""s copending application Ser. No. 07/529,241 discloses and claims a cut-resistant composite yarn utilizing a high strength yarn or fiber strand or component, made from Vectra liquid crystal polymer sold by Hoechst Celanese Corporation, Charlotte, N.C., under the name Vectran HS. That yarn or fiber has substantially the same strength as high strength aramid fiber sold under the name Kevlar. Heretofore, in applicant""s experience, normal strength fibers, when used in composite yarns, have not imparted as great a cut-resistance, along with other desirable characteristics, as high strength fibers have.
The present invention provides a cut-resistant, knittable composite yarn that utilizes a yarn or fiber strand or component of normal strength, made from Vectra liquid crystal polymer, to provide a composite yarn of comparable high cut-resistance to composite yarns of similar construction that utilize high strength synthetic yarn or fiber. The yarn or fiber utilized in the invention is a high performance but normal strength multifilament yarn sold by Hoechst Celanese Corporation, Charlotte, N.C., under the name Vectran M. Normal strength spun yarn made from Vectra is also contemplated. For purposes of definition, normal strength fibers or yarns are those having a tenacity of no more than 10 grams per denier (gpd) and high strength yarns or fibers are those having a tenacity greater than 10 grams per denier, and typically 20 grams per denier or greater (e.g., Kevlar, Spectra and Vectran HS all have a tenacity greater than 20 grams per denier). High strength yarns or fibers also have higher tensile modulus than normal strength fibers, for example, at least 500 grams per denier.
Vectran M has a tenacity of about 9 grams per denier and a tensile modulus of about 425 grams per denier. It has better abrasion resistance than high strength aramid fiber such as Kevlar and significantly better heat resistance than high strength stretched polyethylene fiber, such as Spectra, thus overcoming a different shortcoming of each of Kevlar and Spectra for use in a cut-resistant yarn used for apparel and particularly for cut-resistant gloves. At the same time, quite surprisingly, this normal strength synthetic material provides the substantial advantages that high strength synthetic fibers such as Kevlar, Spectra and Vectran HS have over other normal strength materials in terms of cut-resistance and other characteristics in a composite yarn. Thus, knit fabric suitable for gloves and other safety garments utilizing Vectran M fiber not only has comparable cut-resistance, but also has greater resistance to self-abrasion than similar fabric made with aramid fiber or a combination of aramid and nylon fiber, yet is itself nonabrasive and comfortable to wear. Further, such fabric can be laundered at high temperatures conventionally used for industrial fabrics without degrading the fabric, as occurs with cut-resistant fabric made from yarn that includes high strength stretched polyethylene. In addition, Vectran M has comparable or lower elongation under load to that of high strength fibers, which is advantageous when used in combination with a wire core strand in forming a composite yarn because it protects the wire strand from being broken during knitting or other sharp bending of the composite yarn. Vectran M is consideraby less expensive than Vectran HS, presently about one-half the price.
The present invention provides cut-resistant yarn suitable for machine knitting. Preferred constructions are comprised of a core, a wrapping about the core and another, i.e., second, wrapping about the first and wound in the opposite direction, at least one of said core, first wrapping and second wrapping being comprised of liquid crystal polymer fiber having a tenacity of no more than 10 grams per denier. The denominations such as xe2x80x9cfirstxe2x80x9d wrapping and xe2x80x9csecondxe2x80x9d wrapping as used above and in the claims are to differentiate plural wrappings and do not alone indicate that those wrappings are necessarily the first or second relative to the core. Advantageously, neither the core nor the wrappings need comprise a high strength synthetic fiber for the composite yarn to obtain high cut-resistance. Cut-resistance can be enhanced by including a flexible metal strand i.e., wire, as part of the yarn, either as a core element or as a wrapping.
One preferred cut-resistant yarn suitable for machine knitting constructed in accordance with the invention has a core comprised of synthetic fiber and means bundling the core fiber; a wrapping of wire about the bundled core; and two wrappings of synthetic fiber, each wound in an opposite direction over the wrapping of wire; said synthetic fiber of one of said synthetic fiber wrappings or the core or both being a liquid crystal polymer having a tenacity of no more than 10 grams per denier. In a preferred embodiment the means bundling the core fiber comprises two relatively low denier synthetic wrappings each wound in an opposite direction.
Another preferred construction of a cut-resistant yarn embodying the invention has a core having glass fiber, and wrappings about the core, one or preferably two of said wrappings comprising a liquid crystal polymer fiber having a tenacity of no more than 10 gram per denier. Advantageously this yarn has and other preferred yarns have a covering wrap of nylon or polyester.
If a high strength cut-resistant synthetic fiber is desired in the yarn along with a normal strength liquid crystal polymer fiber, e.g., to impart a characteristic not common to the normal strength liquid crystal polymer, it can be selected from, e.g., high strength aramid such as Kevlar 29, high strength stretched polyethylene such as Spectra, and high strength liquid crystal polymer such as Vectran HS.
A further embodiment of the invention utilizes, in place of a strand or strands of flexible metal wire as found e.g. in the above-described embodiments, a limited number of filaments of significant denier (for example, 1 to 50 filaments of a denier of from 10 to 500 each) of liquid crystal polymer fiber having a tenacity of no greater than 10 grams per denier.
The invention further provides a cut-resistant machine-knitted article of apparel, one such article being a flexible glove, at least in part made of yarn having a construction as referred to above.
A glove or other article of apparel utilizing a preferred yarn construction has not only high resistance to cutting, but also good wear qualities and comfort, does not take a set during use, is non-abrasive, provides a good appearance, and is cleanable and long wearing.
The above and other features and advantages of the invention will become more apparent from the detailed description that follows.